The Hipercor bombing did not arrive without warning. In the two years before the attack, ETA had detonated six car bombs across Barcelona, killing three people. Across Spain, the violence had been intensifying. The country's previous deadliest terrorist attack, the 1985 El Descanso bombing in Madrid, had killed eighteen. ETA's own worst prior attack, a 1986 car bomb on Madrid's Plaza Republica Dominicana, had killed twelve civil guards and injured thirty-two. Barcelona, Spain's second-largest city and the capital of Catalonia, had become a target precisely because of its prominence -- striking there sent a message that no corner of Spain was beyond reach. Just nine days before the Hipercor blast, ETA's political wing Herri Batasuna had received its highest-ever vote share in European Parliament elections, becoming the most-voted party in the three Basque provinces. The political and violent wings of the movement were operating in tandem.

Three members of ETA's so-called Barcelona Commando carried out the attack: Josefa Ernaga, Domingo Troitino, and Rafael Caride Simon, acting on orders from ETA leader Santiago Arrospide Sarasola, known as Santi Potros. They placed an incendiary device inside the store's parking structure. Telephone warnings were phoned in before the explosion, but controversy has surrounded them ever since. Police said the warning came only minutes before the blast. Store security guards and police officers were searching the building when the bomb went off. The explosion ripped through the lower levels, and fire engulfed much of the structure. Among the twenty-one dead were women and children -- ordinary people whose only connection to the Basque conflict was that they had chosen to shop on a Friday afternoon.

The condemnation was nearly universal. Even some leaders within Herri Batasuna, ETA's own political front, felt compelled to publicly denounce the attack. For many Basques who had sympathized with the separatist cause, Hipercor became an inflection point. As The Independent noted after the eventual arrest of bomber Caride Simon in 1993, the attack "was seen by many as a turning point in the organisation's fortunes, its cold-blooded murder of women and children sickening many Basques who until then had sympathised with the group's aims." The violence had crossed a line that even ideological commitment could not excuse. Support for ETA's methods began a long, irreversible decline.

The perpetrators were eventually brought to account, though the process took years. Troitino and Ernaga were detained on 9 September 1987, less than three months after the attack. In October 1989, both received sentences of 794 years in prison and fines exceeding one billion pesetas. Caride Simon, identified as the former head of the Barcelona Commando and the planner of the attack, evaded capture until 1993. On 23 July 2003, he was sentenced to 790 years for carrying out the bombing. Santi Potros, who had ordered it, received the same sentence. The numbers are symbolic under Spanish sentencing law -- no one serves 790 years -- but they reflect the weight the courts placed on what had happened. Today, the site of the former Hipercor store in Barcelona's Sant Andreu neighborhood carries the memory of twenty-one lives ended on an ordinary Friday, a reminder of how terrorism's violence falls hardest on those farthest from the conflict.